Assessing the risk of using pesticides for the environment in general, and for groundwater in particular, necessitates prediction of pesticide migration. For this purpose, mathematical models of pesticide behavior are utilized, which must be parameterized and calibrated based on experimental data to make them perform properly. The behavior of the pesticide cyantraniliprole was examined in a long-term lysimetric experiment. The MACRO 5.2 dual porosity model was calibrated based on the percolate and the levels of pesticides in the soil profile and percolate. Despite employing experimentally verified soil parameters and pedotransfer functions (PTF), the model must be calibrated for percolation. This is due to the model’s properties as well as the complexity of the soil as an object of study, and its pore space, which is subject to daily and annual fluctuations. It is the parameters that describe the structure of the pore space that need to be calibrated. Calibrating for pesticide concentrations required a minor revision of the sorption and transformation rates, as well as an increase in the dispersivity and ASCALE values.

The article discusses issues related to the development of pesticide modeling in the environment and its use in order to regulate the circulation of pesticides. As the study of the literature and the author's experience in using mathematical models shows, the main problem and source of errors in modeling is the quality of the input data for the soil block of the model, as well as those characterizing the properties of the pesticide. Using the results of a carefully conducted lysimetric experiment to study the migration of cyantraniliprole outside the soil profile, as well as auxiliary studies, the influence of hydrodynamic dispersion on the behavior of the insecticide and the results of modeling is shown. The parameters of its non-equilibrium sorption by the soil were calculated according to the data of the laboratory experiment investigating the dynamics of decomposition of cyantraniliprole. The article confirms the need to take these processes into account when modeling the transport of pesticides.

Results of the 60-year research on soil physical properties at the large lysimeters of the Experimental Soil Station of Moscow State University are discussed. The main studied issues include the elements of soil water balance, soil evolution, soil temperature regime, and transport of various substances within the soil profile. The long-term changes in soil texture, soil mineralogy, and organic carbon content have been observed. The horizon sequence in the soil profile affects the intensity of drainage flux and its stabilization in the long-term aspect. The amount of the transit transfer of substances in different soil profiles depends on both profile structure and upper boundary conditions.

Standardized exposure scenarios are important in pesticide authorization procedures. They are used for the estimation the effects of pesticides to soil organisms. Scenarios are needed for evaluation the pesticide concentrations in soil profile. Nine Russian scenarios for exposure assessment were drafted. These scenarios were implemented as input files to the pesticide fate model PEARL. To evaluate the influence of the soil and weather conditions of the scenarios on the level of pesticide in soil, the model PEARL was used to calculate the annual maximum (at the day of application) and 56-day areic content and concentration of test compounds in the soil during long-term pesticide application (for 20 years). It appears the content differences between the nine regulatory zones were no more than a factor of two. These differences were comparatively small in view of the considerable variations in climate and soil characteristics between these zones. Calculations showed the highest pesticide content was observe in Novosibirsk, and the lowest ones were in Krasnodar and Saratov.

The results of the incubation laboratory experiment showed that the decomposition of cyantraniliprole is bi-phasic and the rapid decomposition in the period after the application of the pesticide is accompanied by a subsequent slowdown of this process. The use of the biexponential equation increased the accuracy of the description of the dynamics of decomposition of cyantraniliprole, as evidenced by the static indices. The bi-exponential equation coefficients were used to calculate the parameters of non-equilibrium sorption. The obtained parameters served as input data for the PEARL model. Modelling the migration of cyantraniliprole with considering aged sorption, showed a significant decrease in the predicted concentrations of the pesticide in percolate.

The sorption of the new insecticide cyantraniliprole was studied by the batch equilibrium method. The study of quantitative characteristics of cyantraniliprole sorption by the soils of different types showed that this process is well described by linear isotherms. According to obtained values of K-oc, cyantraniliprole belongs to medium-mobility active substances of pesticides. The sorption value of cyantraniliprole was closely correlated with the content of organic carbon and clay. The regression equation of the dependence of K-d on soil organic carbon content was obtained.

The agrosoddy-podzolic soil (Eutric Albic Glossic Retisol (Abruptic, Loamic, Aric, Cutanic)) is typical for Moscow Oblast and is used for agricultural purposes, resulting in use of various agrochemicals and pesticides. The presence of macropores and cracks in such soils leads to preferential water and substance transfer and nonequilibrium conditions. Therefore, it is important to study the numerical characteristics of the pore space of soils to adjust mathematical models of substance transfer. Undisturbed soil monoliths 10 cm in diameter taken from Ap (from 0 to 30 cm) and E, BE horizons (from 30 to 50 cm) were investigated under the field moisture conditions and after saturation using the tomographic core analyzer RKT-180 with the resolution of 200 μm/pixel. Using the X-ray computer tomography, it has been established that the plough layer of the agrosoddy-podzolic soil contains over 7% of macropores larger than 1 mm, while the subsurface layer has a porosity of about 3%. After saturation, some of the inter-aggregate pores overlap, which leads to a decrease in the total porosity to 4% in the upper and 2% in lower horizons, as well as increase in the average pore diameter. The number of macropores determined by tomographic analysis is one third higher than the values calculated using pedotransfer functions for this soil. The data obtained in this paper are recommended for use in national scenarios of migration of substances (pesticides, agrochemicals, salts) in soils.

Metribuzin is a mobile pesticide widely used in agriculture and has great potential for soil migration. In addition, weather and soil conditions in the non-chernozem zone of Russia contribute to the movement of pesticides in the soil. The behaviour of metribuzin was studied in a lysimetric experiment. The experiment was carried out at the lysimeters of the Soil Research Station of Moscow State University from June 2016 to December 2017. Mertribuzin was applied in lysimeters in maximum recommended and eightfold rates two years in a row. Used in the recommended rate, metribuzin was detected in the samples of lysimetric water once at a concentration of 14 µg L-1 (6% of the samples analyzed). Applied in the eightfold rate, it was detected in 39.5% of samples, the maximum concentration was 180 µg L-1. The experiment revealed that metribuzin is able to leach bottom of the soil profile. The concentration of metribuzin found in the variant with the recommended rate is lower than the hygienic index adopted in Russian Federation for metribuzin, which indicates that the risk of metribuzin application for people is low.

The phenomenon of preferential migration of substances can increase the risk of pesticides. In the first year of the experiment, in 7 days after application cyantraniliprole penetrated to a depth of 25 cm in agrosoddy-podzolic soil. In the next year on the 7th day after application the pesticide was detected at a depth of 15 cm. The pesticide migrated deeper than the unconfigured PERL model took into account. The calibration of the PERL model by using experimental data (soil experimental support) allowed to reduce the error of prediction. The obtained data can be used to create new standard soil and climate scenarios for pesticide leaching models.

The predisposition of the region to groundwater pollution by pesticides depends on climatic and soil factors, characteristics of the aquifer system, the type of the territory management, physicochemical properties of used pesticides and timing of their application. The applying of computer models for vulnerability assessment allows to consider the influence of factors affecting the migration of substances through the soil profile. Agricultural districts of Russia were grouped by basic climatic parameters -average annual temperatures and rainfall. 9 large regions with uniform climatic characteristics were obtained. The combination of climatic and soil parameters of each region made up a standard scenario, which was implemented as input files to the pesticide fate model PEARL. As an indicator of the vulnerability of groundwater to pesticide contamination, we used the predicted weighted average annual pesticide concentrations in leachate at a depth of 1 m. Calculations showed the highest vulnerability was in Nizhny Novgorod, Moscow, Pskov, Vladivostok, intermediate one - in Novosibirsk, and the lowest ones - in Kurgan, Saratov, Kursk and Krasnodar.

Mobility of cyanthraniliprole, paclobutrazol and metribuzin was investigated on large lysimeters of the Experimental Soil Station of Moscow State University. Pesticides were applied in recommended and tenfold rates for cyantraniliprole and paclobuyrazol and recommended and eightfold rates for metribuzin. All three pesticides were detected in leachate. Cyantraniliprole was detected in most water samples analyzed. The maximum concentrations of cyanthraniliprole in the leachate were 2.6 and 12.5 mu g L-1 in lysimeters with recommended and tenfold rates, respectively. Paclobutrazol was found 3 and 7 times during the year after application in the lysimeter with recommended and increased rates in concentrations up to 26 mu g L-1. Used in accordance with the regulation, metribuzin in leachate was detected once, in eightfold rate - 73% of water samples; maximum concentration was 180 mu g L-1. The migration risk into groundwater of all three studied pesticides is assessed as high, risk for people as low, risk for aquatic organisms as high. Risk and danger assessment based on simulation with model PEARL and mobility indexes showed high agreement with the assessment according to the experiment.

The behaviour of cyantraniliprole was studied in a lysimetric experiment. The experiment was carried out at the lysimeters of the Soil Research Station of Moscow State University from June 2015 to December 2018. The soil of lysimeter is soddy-podzolic silt loam. The insecticide was applied at the recommended and tenfold rates in 2015 and 2016. The maximum depth of migration of cyantraniliprole in the soil profile was 35 cm in October 2015 and 40 cm in October 2016. Cyantraniliprole was found in the leachate of lysimeter water 2 weeks after its first application in 2015 and continued until the end of 2018, that is, 2 years after the last treatment. Cyantraniliprole was found in most of the water samples analyzed. The maximum concentrations of cyantraniliprole in the leachate were 12.5 and 2.6 μg L−1 in lysimeters with tenfold and recommended doses, with mean values of - 1.7 and 0.6 μg L−1, respectively.

Реферат.В настоящее время список пестицидов, по которым Росгидромет проводит мониторинг, состоит из 23 соединений, среди которых только семь разрешены для применения в России и входят в "Государственный каталог пестицидов и агрохимикатов".Предложена пошаговая расчетная процедура для формирования приоритетного перечня пестицидов, подлежащих мониторингу в грунтовых водах.Для этого с помощью модели PEARL определяются прогнозные концентрации пестицидов в стоке грунтовых вод на глубине одного метра и проводится оценка риска миграции пестицидов в грунтовые воды (по величине прогнозной концентрации), оценка риска для млекопитающих (путем сравнения прогнозных концентраций с ПДК) и водных организмов (сравнивая с токсичностью для гидробионтов).По результатам расчетов в список вошло 47 пестицидов из 180-ти, разрешенных к применению в РФ.Сформулированы основные принципы определения перечня пестицидов, содержание которых необходимо контролировать в грунтовых водах: избирательный

Mathematical models of solute movement in soils are used as management means for assessing the migration of agrochemicals and calculating environmental risks. In these models, the soil block includes the soil values of dispersivity length or solute diffusivity as one of the main parameters. Under laboratory conditions, this parameter was determined experimentally in soil columns by recording the dynamics of the effluent concentration and solving inverse problems. A direct experimental method of field determination based on the movement of marker solution was tested. For the prediction, risk calculation, and management of pesticide application using physically based mathematical models, the following stepwise procedure is recommended: (1) model parameterization based on experimental soil properties; (2) use of the field dispersivity length, which was 3–11 cm for the 0- to 40-cm layer, exceeded 12 cm for deeper fissured BEL and BT (40- to 60-cm) horizons with prismatic structure, and had a median value of 21 cm in layers below 60 cm in experiments on an agrosoddy-podzolic soil (Eutric Albic Glossic Retisol (Abruptic, Loamic, Aric) (WRB, 2014) from Moscow oblast.

Modern agriculture is impossible without the use of plant protection products.In addition to the expected effect of protection from pests, diseases and weeds, the use of pesticides often has an adverse effect on the environment and nontarget organisms.In particular, numerous studies have revealed the discovery of pesticide residues in groundwater around the world.For regulation purpose, in order to assess pesticide environmental risks in Russia, the experimental data obtained in the EU is used.The climate in Russia is colder with significantly higher water percolation than in Europe, which leads to a higher risk of pesticide migration to groundwater.This is also facilitated by the movement of plant protection products with preferential water flows through macropores and cracks.The purpose of the research was to study the migration of the insecticide cyantraniliprole in the soil profile.Cyantraniliprole is a moderately persistence (DT 50 =34.4days) medium-mobility (К ос =241) substance.The experiment was carried out at the lysimeters of the Soil Research Station of Moscow State University from June 2015 to May 2017.The soil of lysimeter is soddy-podzolic silt loam.The insecticide was used at the recommended (0.4 kg ha -1 ) and tenfold rates in June 2015 and then in June 2016.Water leachate from lysimeter was collected every week.Soil samples were collected every 5 cm till depth of 50 cm in spring and autumn.Cyantraniliprole was analysed by HPLC.Detection limits of the analytical method was 0.5 μg / L and 2.5 μg / kg for water and soil respectively.The average annual air temperature in the years of the experiment was close to the average long-term values.The amount of precipitation in 2016 exceeded the mean annual value by 90 mm, and in the summer period of 2016 -by 121 mm.In 2015, average precipitation values for the year and for the seasons were close to the average annual parameters.However, in the summer of 2015 heavy showers with a daily rainfall rate exceeding a quarter of the monthly norm were observed.The maximum depth of migration of cyananthraniliprole in the soil profile was 35 cm in October 2015 and 40 cm in October 2016.Despite the fact that cyanantraniliprole is a medium-persistence, one year after the second treatment (in May 2017), a rather large concentration of the pesticide (near 35% of applied rate) was in the soil, which distributed to a depth of 30 cm, with a maximum in the upper 5-cm layer.Cyantraniliprole was found in the leachate of lysimeter water 2 weeks after first application in both lysimeters (with the recommended and tenfold doses), the pesticide concentrations were 0.8 and 1.5 μg / L respectively.This was facilitated by the precipitation of several showers with rainfall more than 20 mm.This indicates a high mobility of the pesticide in this soil and a large influence of rainfall on the rapid arrival of the pesticide beyond the soil profile.Cyantraniliprole was found in most of the analyzed water samples.The pesticide in the water leachate wasn't found in 2015 in 22% of the samples at the recommended dose and in 6% of the samples at a tenfold dose.In 2016 and 2017, cyantraniliprole was detected in all the selected aqueous samples.

Optimal solutions found with mathematical models on agricultural chemical application depend on the interrelated complexity of the model and the required accuracy: the larger the number of complexly determined parameters, the more difficult the model. As a result, the calculation accuracy decreases. This problem should be solved with understanding of the physical aspects of the main soil processes of pesticide transport, experimental determination of their parameters, and adjustment of models in parallel with a substantiated reduction in their complexity. Experimental study of the physical processes with the PEARL 4.4.4 model and analysis of its sensitivity to the input parameters has shown which characteristics of experimental control are the most significant for water and pesticide migration. A filtration experiment with KCl made it possible to determine the dispersivity length and the filtration coefficient. As a result, a description of pesticide migration with fast water flows was introduced into the equation and the prediction accuracy increased.

The water block of physically founded models of different levels (chromatographic PEARL models and dual-porosity MACRO models) was parameterized using laboratory experimental data and tested using the results of studying the water regime of loamy soddy-podzolic soil in large lysimeters of the Experimental Soil Station of Moscow State University. The models were adapted using a stepwise approach, which involved the sequential assessment and adjustment of each submodel. The models unadjusted for the water block underestimated the lysimeter flow and overestimated the soil water content. The theoretical necessity of the model adjustment was explained by the different scales of the experimental objects (soil samples) and simulated phenomenon (soil profile). The adjustment of the models by selecting the most sensitive hydrophysical parameters of the soils (the approximation parameters of the soil water retention curve (SWRC)) gave good agreement between the predicted moisture profiles and their actual values. In distinction from the PEARL model, the MARCO model reliably described the migration of a pesticide through the soil profile, which confirmed the necessity of physically founded models accounting for the separation of preferential flows in the pore space for the prediction, analysis, optimization, and management of modern agricultural technologies.